NKT cells in HIV-1 infection

Natural killer T （NKT） cells are a unique T cell population that have important immunoregulatory functions and have been shown to be involved in host immunity against a range of microorganisms. It also emerges that they might play a role in HIV-1 infection, and therefore be selectively depleted during the early stages of infection. Recent studies are reviewed regarding the dynamics of NKT depletion during HIV-1 infection and their recovery under highly active antiretroviral treatment （HAART）. Possible mechanisms for these changes are proposed based on the recent developments in HIV pathogenesis. Further discussions are focused on HIV＇s disruption of NKT activation by downregulating CDld expression on antigen presentation cells （APC）. HIV-1 protein Nefis found to play the major role by interrupting the intracellular trafficking of nascent and recycling CDld molecules.

Structure modifications based on KRN7000 and their SARs in activating NKT cells

α-Galactosylceramides, which can be recognized by natural killer T （NKT） cells, are now attracting more and more attention due to their therapeutic potential in cancer, infection and autoimmune diseases. Advances have been achieved in discovering compounds with better activities and efforts have been made to understand the structure-activity relationships （SARs） of these NKT cell ligands. In this review, we discuss the structure modifications based on KRN7000, the principal glycolipid used in the study of NKT cell stimulation, and the SARs based on these modified structures.

EBV-Induced Human CD8^＋ NKT Cells Synergise CD4^＋ NKT Cells Suppressing EBV-Associated Tumours upon Induction of Thl-Bias

CD8^＋ natural killer T （NKT） cells from EBV-associated tumour patients are quantitatively and functionally impaired. EBV-induced CD8^＋ NKT cells drive syngeneic T cells into a Thl-bias response to suppress EBV-associated malignancies. IL-4-biased CD4^＋ NKT cells do not affect either syngeneic T cell cytotoxicity or Th cytokine secretion. Circulating mDC1 cells from patients with EBV-associated malignancies impair the production of IFN-T by CD8^＋ NKT cells. In this study, we have established a human-thymus-SCID chimaera model to further investigate the underlying mechanism of EBV-induced CD8^＋ NKT cells in suppressing EBV-associated malignancies. In the human-thymus-SCID chimera, EBV-induced CD8^＋ NKT cells suppress EBV-associated malignancies in a manner dependent on the Thl-bias response and syngeneic CD3^＋ T cells. However, adoptive transfer with CD4^＋ NKT cells alone inhibits T cell immunity. Interestingly, CD4^＋ NKT cells themselves secrete high levels of IL-2, enhancing the persistence of adoptively transferred CD8^＋ NKT cells and T cells, thereby leading to a more pronounced T cell anti-tumour response in chimaeras co-transferred with CD4^＋ and CD8^＋ NKT cells. Thus, immune reconstitution with EBV-induced CD4^＋ and CD8^＋ NKT cells synergistically enhances T cell tumour immunity, providing a potential prophylactic and therapeutic treatment for EBV-associated malignancies.

Lactic acid in tumor microenvironments causes dysfunction of NKT cells by interfering with mTOR signaling

Cellular metabolism has been shown to regulate differentiation and function of immune cells. Tumor associated immune cells undergo phenotypic and functional alterations due to the change of cellular metabolism in tumor microenvironments. NKT cells are good candidates for immunotherapies against tumors and have been used in several clinical trials. However, the influences of tumor microenvironments on NKT cell functions remain unclear. In our studies, lactic acid in tumor microenvironments inhibited IFN？ and IL4 productions from NKT cells, and more profound influence on IFN？ was observed. By adjusting the pH of culture medium we fiu-ther showed that, dysfunction of NKT cells could simply be induced by low extracellular pH. Moreover, low extracellular pH inhibited NKT cell functions by inhibiting mammalian target of rapamycin （roTOR） signaling and nuclear translocation of promyelocytic leukemia zinc-finger （PLZF）. Together, our results suggest that tumor acidic microenvironments could interfere with NKT cell functions through metabolic controls.

CD205-TLR9-IL-12 axis contributes to CpG-induced oversensitive liver injury in HBsAg transgenic mice by promoting the interaction of NKT cells with Kupffer cells

Gut-derived bacterial products contribute to liver inflammation and injury during chronic hepatitis B virus infection;however,the underlying mechanisms remain obscure.In this study,hepatitis B surface antigen transgenic(HBs-Tg)mice and their wild-type(WT)control C57BL/6 mice were injected with CpG-oligodeoxynucleotides(ODNs)to mimic the translocation of gut microbial products into the systemic circulation.We found that,compared with the WT mice,the HBs-Tg mice were oversensitive to CpG-ODN-induced liver injury,which was dependent on natural killer T(NKT)cells.CpG-ODN injection enhanced the expression of Fas ligand(FasL)on NKT cells.In addition,hepatocytes from the HBs-Tg mice expressed higher levels of Fas than did those from the WT mice,which was further augmented by CpG-ODN.Interaction of Fas and FasL was involved in the cytotoxicity of NKT cells against hepatocytes in the HBs-Tg mice.Moreover,Kupffer cells in the HBs-Tg mice expressed higher levels of CD205 and produced greater amounts of interleukin(IL)-12 than did those in the WT mice.Finally,the depletion of Kupffer cells,neutralization of IL-12 or specific silencing of CD205 on Kupffer cells significantly inhibited CpG-ODN-induced liver injury and NKT activation in the HBs-Tg mice.Our data suggest that CD205-expressing Kupffer cells respond to CpG-ODNs and subsequently release IL-12 to promote NKT cell activation.Activated NKT cells induce liver damage through the Fas signaling pathway in HBs-Tg mice.

Inhibition effect of natural killer T cells on transplantation hepatocellular carcinoma in mice

Objective:The aim of this study was to investigate the inhibition effect of natural killer T(NKT) cells on transplantation hepatocellular carcinoma in mice.Methods:α-galactosylceramide(α-GalCer)-pulsed DC and Hep S were prepared as stimulus.Hepatoma xenograft model was established and mice were randomly divided into 4 groups(n=13 each group):(1) control group,intravenous injection of the same volume of saline.(2) mature DC group,intravenous injection of mature DC cells(4×106 cells).(3) α-GalCer-pulsed HepS group,intravenous injection of α-GalCer-pulsed HepS(4×106 cells).(4) α-GalCer-pulsed mature DC group,intravenous injection of α-GalCer-pulsed DC(4×106 cells).The changes of tumor volume in mice and survival period were measured every 2 days.Percentage of NKT cells in spleens and cytotoxicity of spleen cells were detected by flow cytometry.Tumor tissues were analyzed by histopathological examination.Results:In α-GalCer-pulsed Heps and DC groups,the average survival period was prolonged and tumor volume was markedly decreased,spleen cells and NKT cells were significantly increased,and tumor necrosis was evident,compared to the control group.Conclusion:α-GalCer-pulsed DC and HepS could activate NKT cells in vivo,also increase NKT cells cytotoxicity,inhibit the growth of hepatomas and prolong survival period.

Immune cells in term and preterm labor

Labor resembles an inflammatory response that includes secretion of cytokines/chemokines by resident and infiltrating immune cells into reproductive tissues and the maternal/fetal interface. Untimely activation of these inflammatory pathways leads to preterm labor, which can result in preterm birth. Preterm birth is a major determinant of neonatal mortality and morbidity; therefore, the elucidation of the process of labor at a cellular and molecular level is essential for understanding the pathophysiology of preterm labor. Here, we summarize the role of innate and adaptive immune cells in the physiological or pathological activation of labor. We review published literature regarding the role of innate and adaptive immune cells in the cervix, myometrium, fetal membranes, decidua and the fetus in late pregnancy and labor at term and preterm. Accumulating evidence suggests that innate immune cells （neutrophils, macrophages and mast cells） mediate the process of labor by releasing pro-inflammatory factors such as cytokines, chemokines and matrix metalloproteinases. Adaptive immune cells （T-cell subsets and B cells） participate in the maintenance of fetomaternal tolerance during pregnancy, and an alteration in their function or abundance may lead to labor at term or preterm. Also, immune cells that bridge the innate and adaptive immune systems （natural killer T （NKT） cells and dendritic cells （DCs）） seem to participate in the pathophysiology of preterm labor. In conclusion, a balance between innate and adaptive immune cells is required in order to sustain pregnancy; an alteration of this balance will lead to labor at term or preterm.

NKT cell subsets as key participants in liver physiology and pathology

Natural killer T （NKT） cells are innate-like lymphocytes that generally recognize lipid antigens and are enriched in microvascular compartments of the liver. NKT cells can be activated by self- or microbial-lipid antigens and by signaling through toll-like receptors. Following activation, NKT cells rapidly secrete pro-inflammatory or anti- inflammatory cytokines and chemokines, and thereby determine the milieu for subsequent immunity or tolerance. It is becoming clear that two different subsets of NKT cells-type I and type II--have different modes of antigen recognition and have opposing roles in inflammatory liver diseases. Here we focus mainly on the roles of both NKT cell subsets in the maintenance of immune tolerance and inflammatory diseases in liver. Furthermore, how the differential activation of type I and type II NKT cells influences other innate cells and adaptive immune cells to result in important consequences for tissue integrity is discussed. It is crucial that better reagents, including CDld tetramers, be used in clinical studies to define the roles of NKT cells in liver diseases in patients.

M2-specific reduction of CD1d switches NKT cell-mediated immune responses and triggers metaflammation in adipose tissue

Metaflammation is responsible for several metabolic syndromes,such as type 2 diabetes.However,the mechanisms by which metabolic disorders trigger metaflammation remain unclear.We identified a cell type-specific downregulation of CD1d expression in M2 macrophages during the progression of obesity prior to the onset of inflammation in visceral adipose tissues.A reduction in CD1d expression influenced the ability of M2 macrophages to present antigens and caused a change in antigen-presenting cells from M2 macrophages to M1 macrophages.With CD1d conditional knockout(KO)mice,we further demonstrated that natural killer T(NKT)cell activation by M2 macrophages inhibited metaflammation and insulin resistance by promoting Th2 responses and M2 polarization in visceral adipose tissues of obese mice,whereas NKT cell activation by M1 macrophages exacerbated metaflammation and insulin resistance by promoting Th1 responses and inhibiting M2 polarization.Our results suggest that an M2-specific reduction of CD1d is an initiating event that switches NKT cell-mediated immune responses and disrupts the immune balance in visceral adipose tissues in obese mice.

Boosting the immune response： the use of iNKT cell ligands as vaccine adjuvants

Natural killer T （NKT） cells comprise a small, but important T cell subset and are thought to bridge the innate and adaptive immune responses. The discovery of NKT cells and extensive research on their activating ligands have paved the way for modulation of these potent immunoregulatory cells in order to improve the outcome of various clinical conditions. Efforts to modulate NKT cell effector functions have ranged from therapy for influenza to anti- tumor immunotherapy. These approaches have also led to the use of NKT cell agonists such as a-Galactosylceramide （a- GalCer） and its analogs as vaccine adjuvants, an approach that is aimed at boosting specific B and T cell responses to a vaccine candidate by concomitant activation of NKT cells. In this review we will provide a comprehensive overview of the efforts made in using a-GalCer and its analogs as vaccine adjuvants. The diverse array of vaccination strategies used, as well as the role of NKT cell activating adjuvants will be discussed, with focus on vaccines against malaria, HIV, influenza and tumor vaccines. Collectively, these studies demonstrate the efficacy of NKT cell-specific agonists as adjuvants and suggest that these compounds warrant serious consideration during the development of vaccination strategies.

The Roles of Innate Immune Cells in Liver Injury and Regeneration

For predominant abundance with liver-specific Kupffer cells, natural killer （NK） cells, and natural killer T （NKT） cdls and their rapid responses to several stimuli, the liver is considered as an organ with innate immune features. In contrast to their roles in the defense of many infectious agents like hepatitis viruses and parasites, hepatic innate immune cells are also involved in the immunopathogenesis of human clinical liver diseases and several murine hepatitis models such as concanavalin A （Con A）, lipopolysaccharide （LPS）, or polyinosinic-polycytidylic acid （Poly I：C）-induced liver injury. In this review, the destructive roles of NK cells, NKT cells and Kupffer cells in the processes of immune-mediated liver injury and regeneration will be discussed, and some putative mechanisms involving the impairment of liver regeneration caused by activated hepatic innate immune cells are also proposed.

The Role of Innate Immune Cells in the Response of Heat-Treated Mycobacterium tuberculosis (M.tb) Antigens Stimulating PBMCs

The proliferation response of γδT cells to the antigen from heat-treated Mycobacterium tuberculosis H37Ra (M.tb Ag)was used as a good model in γδT cell research.From preliminary research it is found that activated NK cells positively elevated γδT cells proliferation after simulating PBMCs with M.tb Ag.To investigate different behaviors of NK cells,γδNKT cells,γδT cells and relationships between these cell subsets,activation and proliferation of different cell subsets of PBMCs in response to M.tb Ag were analyzed.We demonstrated that NK cells,γδNKT cells and γδT cells could be activated after stimulation with M.tb Ag.γδNKT cells and γδT cells proliferated while the number of NK cells decreased after 11 day-simulation with M.tb Ag.Meanwhile,at the early time of stimulation the cytotoxicity of PBMCs was enhanced.Cellular & Molecular Immunology. 2004;1(6):467-470.

TRAF3IP3 at the trans-Golgi network regulates NKT2 maturation via the MEK/ERK signaling pathway

Thymic natural killer T(NKT)2 cells are a subset of invariant NKT cells with PLZF^(hi)GATA3^(hi)IL-4^(+).The differentiation of NKT2 cells is not fully understood.In the present study,we report an important role of TRAF3-interacting protein 3(TRAF3IP3)in the functional maturation and expansion of committed NKT2s in thymic medulla.Mice with T-cell-specific deletion of TRAF3IP3 had decreased thymic NKT2 cells,decreased IL-4-producing peripheral iNKTs,and defects in response toα-galactosylceramide.Positive selection and high PLZF expression in CD24^(+)CD44^(−) and CCR7^(+)CD44^(−) immature iNKTs were not affected.Only CD44^(hi)NK1.1^(−) iNKTs in Traf3ip3^(−/−) mice showed reduced expression of Egr2,PLZF,and IL-17RB,decreased proliferation,and reduced IL-4 production upon stimulation.This Egr2 and IL-4 expression was augmented by MEK1/ERK activation in iNKTs,and TRAF3IP3 at the trans-Golgi network recruited MEK1 and facilitated ERK phosphorylation and nuclear translocation.LT βR-regulated bone marrow-derived nonlymphoid cells in the medullary thymic microenvironment were required for MEK/ERK activation and NKT2 maturation.These data demonstrate an important functional maturation process in NKT2 differentiation that is regulated by MEK/ERK signaling at the trans-Golgi network.

Transcription factor YY1 is essential for iNKT cell development

Invariant natural killer T(iNKT)cells develop from CD4+CD8+double-positive(DP)thymocytes and express an invariant Vα14–Jα18 T-cell receptor(TCR)α-chain.Generation of these cells requires the prolonged survival of DP thymocytes to allow for Vα14–Jα18 gene rearrangements and strong TCR signaling to induce the expression of the iNKT lineage-specific transcription factor PLZF.Here,we report that the transcription factor Yin Yang 1(YY1)is essential for iNKT cell formation.Thymocytes lacking YY1 displayed a block in iNKT cell development at the earliest progenitor stage.YY1-deficient thymocytes underwent normal Vα14–Jα18 gene rearrangements,but exhibited impaired cell survival.Deletion of the apoptotic protein BIM failed to rescue the defect in iNKT cell generation.Chromatin immunoprecipitation and deep-sequencing experiments demonstrated that YY1 directly binds and activates the promoter of the Plzf gene.Thus,YY1 plays essential roles in iNKT cell development by coordinately regulating cell survival and PLZF expression.